Abstract: In this study, a composite photocatalyst BiOCl@CNC was prepared by simple stirring with BiOCl at room temperature using nanocellulose (CNC) as a carrier. Comprehensive characterizations (XRD, FT-IR, SEM, TEM, XPS) reveal that the abundant hydroxyl groups in CNC can form strong hydrogen bonds with BiOCl, leading to the creation of numerous oxygen vacancies in the material and thereby significantly enhancing its visible light-driven photocatalytic performance. The performance of the BiOCl@CNC was evaluated using the C-N coupling reaction of benzylamine as the target reaction under visible light, and the underlying mechanism was investigated. The results show that the optimal reaction process is that 1.0 mmol of benzylamine and 20 mg of BiOCl@CNC are added to CH₃CN under an oxygen atmosphere to react for 20 hours using a 30 W white LED lamp as the light source. In the substrate expansion experiments, the BiOCl@CNC exhibits remarkable adaptability and exceptional stability towards reactants with diverse substituents. The free radical capture experiments demonstrate that the electrons can effectively generate superoxide radicals in the presence of oxygen vacancies and subsequently form the ultimate product through amine cation radical intermediates. This study not only expands the application potential of Bi-based composite semiconductors but also presents novel insights for synthesizing N-benzylene butylamine.